Manufacturing method for molded products

Abstract

To provide a method for manufacturing molded products that create an impression similar to the real thing, without resorting to the mixing of multiple types of pellets or the use of coloring agents, etc.SOLUTION: A method for manufacturing a molded product using a cellulosic fiber composite resin includes the steps of: adjusting the cellulosic fiber composite resin so that a difference in flowability is generated depending on a flow point when the cellulosic fiber composite resin flows through a cavity in the mold; clamping the mold; injecting the cellulosic fiber composite resin into the cavity in the mold from one or more gates; and opening the mold to remove the molded product after the cellulosic fiber composite resin has hardened. In the injection process, when the cellulosic fiber composite resin flows in the mold, shear heating caused by the difference in flowability is accompanied by the generation of furfural, a brownish color component.SELECTED DRAWING: Figure 1A

Description

Technical Field

[0001] The present disclosure relates to a molded article using a cellulose fiber composite resin and a method for manufacturing the same.

Background Art

[0002] As a method for manufacturing a woody resin molded article with the texture of wood expressed on the surface, for example, a method of obtaining a woody texture by imparting wood grain by using a colorant to create color unevenness and color shading (such as marble-like molding) is common.

[0003] However, with the above method, although the color of the wood grain can be represented, it is difficult to represent the tactile sensation, texture, and quality due to the fine irregularities on the surface. For this reason, there is a problem that a plastic feeling remains. In response to such a problem, for example, the method shown in Patent Document 1 has been developed. FIG. 4 is a schematic cross-sectional view showing the cross-sectional structure of a vent type extrusion molding machine (hereinafter abbreviated as "extruder") 40 used in the method for manufacturing a woody resin molded article described in Patent Document 1. This extruder 40 includes a cylindrical cylinder 41, a screw 42 provided inside the cylinder 41, a hopper (first hopper) 43 provided at the rear end of the cylinder 41, a vent hole 44 formed at the tip side of the central portion of the cylinder 41, and a die 45 provided at the tip of the cylinder 41 for imparting a desired shape to the pellet melt, and is a known single-screw type extruder.

[0004] A second hopper 46 is connected to the extruder 40 in communication with the vent hole 44, and one of a base material pellet or a woody forming material pellet is supplied and stored in the second hopper 46. Further, a pellet different from the pellet stored in the second hopper 46 is supplied and stored in the first hopper 43 among the base material pellet and the woody forming material pellet.

[0005] When molding is performed using such an extruder 40, pellets supplied from the first hopper 43 are fed into the cylinder 41, where they are heated and melted while being pushed forward by the screw 42. Pellets supplied from the second hopper 46 are fed into the cylinder 41 through the vent hole 44 and supplied to the deep groove 42a of the screw 42. As a result, the internal volume of the cylinder 41 in the deep groove 42a is larger than before the deep groove 42a, creating a sufficient void. Thus, pellets from the second hopper 46 are supplied to this void without being subjected to significant stress from the molten material from the first hopper 43, and are mixed into the molten material from the first hopper 43. The pellets from the second hopper 46 are heated and melted inside the cylinder 41, mixed with the molten pellets from the first hopper 43 by the screw 42, and then pushed out together with the molten pellets from the first hopper 43. The raw material pellets and wood-like forming material pellets are melted and mixed in this manner, then extruded from die 45 to form a wood-like molded product in the desired shape.

[0006] According to this manufacturing method, the base material pellets and the wood-like forming material pellets melt and flow in the molding direction, causing the resins, supported cellulose fine particles (cellulose-based fine particles with surface particles), the first colored pigment, and the second colored pigment to mix unevenly (Figure 5). Furthermore, on the surface of the molded product, for example when molded into a plate shape, the colored areas 20 are streaky, as shown in Figure 6, but are not continuous but intermittent and independent, and their shading and streak thickness are also uneven.

[0007] Furthermore, especially on the surface of the molded product, when the cellulose-based fine particles 11 carrying the white pigment particles 10 in the wood-like forming material pellets come into contact with the colored area 20, the color of the colored area 20 is obscured by the white pigment. As a result, the unevenness of the shading of the colored area 20 (streaky pattern) visible on the surface as shown in Figure 6 increases, making the colored area 20 even closer to a natural wood grain pattern. In addition, especially when titanium dioxide is used as the white pigment, because the cellulose-based fine particles 11 carry thermally and chemically stable titanium dioxide, the decomposition of the cellulose-based fine particles 11 during molding can be suppressed without applying chemical treatments such as alkali treatment to the cellulose-based fine particles 11. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Japanese Patent Application Publication No. 10-305470 [Overview of the Initiative] [Problems that the invention aims to solve]

[0009] However, the method described in Patent Document 1 requires at least two types of pellets—raw material pellets and wood-like forming material pellets—to achieve the desired color variations and shades in order to represent the wood texture. Furthermore, because the two types of materials are fed separately, there are material and equipment constraints, such as the need to use two or more hoppers, resulting in high manufacturing costs. In addition, as described in paragraph 0062 of Patent Document 1, the wood-like forming material pellets to which cellulose fine particles are added constitute 1 to 10 wt% of the supplied pellets, and at least 90 wt% are raw material pellets (including additives). As a result, the wood texture, that is, the fine surface irregularities, gloss, and color variations, are poor. If the proportion of cellulose fine particles added to improve the wood texture is increased, there is a problem that the resin becomes brittle because the cellulose is in the form of fine particles.

[0010] This disclosure aims to solve the aforementioned conventional problems and to provide a method for manufacturing molded products that can produce molded products that closely resemble the real thing without using a mixture of multiple types of pellets or colorants. [Means for solving the problem]

[0011] To achieve the above objective, a method for manufacturing a molded article using a cellulose fiber composite resin according to this disclosure includes the steps of: adjusting the cellulose fiber composite resin so that differences in fluidity occur depending on the flow location as the cellulose fiber composite resin flows through the cavity in the mold; clamping the mold; injecting the cellulose fiber composite resin into the cavity in the mold from one or more gates; and, after the cellulose fiber composite resin has hardened, opening the mold and removing the molded article, wherein the step of injecting the cellulose fiber composite resin is accompanied by the generation of furfural, a browning component, due to shear heating caused by differences in fluidity as the cellulose fiber composite resin flows through the mold. [Effects of the Invention]

[0012] According to the manufacturing method for molded articles described herein, it is not necessary to use multiple types of materials and special molding machines to express the texture, color variations, and grain of wood. Furthermore, the number of wood grains and the intensity of the color can be controlled by devising the structure of the mold. Therefore, it is possible to provide molded articles that are even closer to natural wood than conventional methods, and that are also of high strength. [Brief explanation of the drawing]

[0013] [Figure 1A] This is a schematic perspective view showing the shape of the molded product according to Example 1. [Figure 1B] Figure 1A is a plan view of the molded product. [Figure 1C] This is a cross-sectional view showing the cross-sectional structure as seen in the AA direction in Figure 1A. [Figure 1D] This is a cross-sectional view showing the cross-sectional structure of a modified example, as shown in Figure 1C. [Figure 2-0A]It is a cross-sectional view showing the cross-sectional structure of the flow state of the molten resin in the method for manufacturing a molded product according to Example 1. [Figure 2-0B] It is a cross-sectional view showing the cross-sectional structure of the molten resin cured after Figure 2-0A. [Figure 2-1A] It is a plan view showing the configuration of the molded product according to Example 2. [Figure 2-1B] It is a schematic perspective view showing a portion with a large amount of browning component in the molded product of Figure 2-1A. [Figure 2-1C] It is a schematic perspective view showing the flow transition of the molten resin in the method for manufacturing a molded product according to Example 2. [Figure 2-1D] It is a schematic perspective view showing the flow transition of the molten resin in the method for manufacturing a molded product according to Example 2. [Figure 2-1E] It is a schematic perspective view showing the flow transition of the molten resin in the method for manufacturing a molded product according to Example 2. [Figure 2-1F] It is a schematic perspective view showing the flow transition of the molten resin in the method for manufacturing a molded product according to Example 2. [Figure 2-2A] It is a plan view of a molded product according to a modified example of Example 2. [Figure 2-2B] It is a schematic perspective view showing the appearance of the molded product of Figure 2-2A. [Figure 2-2C] It is a schematic perspective view showing the flow transition of the molten resin in the method for manufacturing a molded product according to a modified example of Example 2. [Figure 2-2D] It is a schematic perspective view showing the flow transition of the molten resin in the method for manufacturing a molded product according to a modified example of Example 2. [Figure 2-2E] It is a schematic perspective view showing the flow transition of the molten resin in the method for manufacturing a molded product according to a modified example of Example 2. [Figure 2-3A] It is a plan view showing the configuration of the molded product according to Example 3. [Figure 2-3B] It is a schematic perspective view showing the flow transition of the molten resin in the method for manufacturing a molded product according to Example 3. [Figure 2-4A] It is a plan view showing the configuration of the molded product according to Example 4. [Figure 2-4B]This is a schematic perspective view showing the flow transition of the molten resin in the manufacturing method of the molded product according to Example 4. [Figure 2-4C] This is a schematic perspective view showing the flow transition of the molten resin in the manufacturing method of the molded product according to Example 4. [Figure 2-4D] This is a schematic perspective view showing the flow transition of the molten resin in the manufacturing method of the molded product according to Example 4. [Figure 2-5A] This is a schematic perspective view showing the flow transition of the molten resin in the manufacturing method of the molded product according to Example 5. [Figure 2-5B] This is a schematic perspective view showing the flow transition of the molten resin in the manufacturing method of the molded product according to Example 5. [Figure 2-5C] This is a schematic perspective view showing the flow transition of the molten resin in the manufacturing method of the molded product according to Example 5. [Figure 2-5D] This is a schematic perspective view showing the flow transition of the molten resin in the manufacturing method of the molded product according to Example 5. [Figure 3A] This is a plan view showing the flow transition of the resin in the manufacturing method of the molded product according to Example 6. [Figure 3B] This is a plan view showing the flow transition of the resin in the manufacturing method of the molded product according to Example 6. [Figure 3C] This is a plan view showing the flow transition of the resin in the manufacturing method of the molded product according to Example 6. [Figure 3D] This is a plan view showing the flow transition of the resin in the manufacturing method of the molded product according to Example 6. [Figure 3E] This is a plan view showing the flow transition of the resin in the manufacturing method of the molded product according to Example 6. [Figure 3F] This is a plan view showing the flow transition of the resin in the manufacturing method of the molded product according to Example 6. [Figure 4] This figure shows a schematic cross-sectional view of the vented extrusion molding machine used in the method for manufacturing wood-like resin molded products described in Patent Document 1. [Figure 5] Figure 4 is a schematic cross-sectional view showing the cross-sectional structure of a molded product manufactured by a vented extrusion molding machine. [Figure 6]Figure 4 is a schematic perspective view showing the appearance of a molded product manufactured using the vented extrusion molding machine shown. [Modes for carrying out the invention]

[0014] <Background leading to this disclosure> Traditionally, achieving a wood-like texture with desired color variations and shading has required material and equipment constraints, such as the need to use a mixture of multiple types of pellets and colorants, and a molding machine with multiple hoppers. On the other hand, the present inventors have knowledge that by thermally denaturing cellulose in a cellulose-based composite resin, browning components such as 2-fluoraldehyde (hereinafter referred to as "furfural") are produced. By controlling the amount of furfural produced, the inventors investigated how to obtain a wood-like texture with desired color variations and shading by controlling the basic color of the molded product while forming natural discoloration and color unevenness that occur due to the aging and growth of natural wood. Specifically, the inventors arrived at a method for manufacturing a molded product according to this disclosure, which includes a step of adjusting the flowability of the cellulose-based fiber composite resin as it flows through the cavity in the mold, so that differences in flow occur depending on the flow location, through ingenuity in the product shape and mold specifications. As a result, it is possible to create shading in specific parts of the molded product and provide a molded product that closely resembles real wood.

[0015] The method for manufacturing a molded article using a cellulose fiber composite resin related to this disclosure is described below.

[0016] A method for manufacturing a molded article using a cellulose fiber composite resin according to the first embodiment includes the steps of: adjusting the cellulose fiber composite resin so that differences in fluidity occur depending on the flow location as the cellulose fiber composite resin flows through the cavity in the mold; clamping the mold; injecting the cellulose fiber composite resin into the cavity in the mold from one or more gates; and, after the cellulose fiber composite resin has hardened, opening the mold and removing the molded article, wherein the step of injecting the cellulose fiber composite resin is accompanied by the generation of furfural, a browning component, due to shear heating caused by differences in fluidity as the cellulose fiber composite resin flows through the mold.

[0017] In the second embodiment, the method for manufacturing a molded article is as described above in the first embodiment, wherein the cellulose fiber composite resin contains cellulose fibers at a concentration of 40 wt% or more, and pellets with a whiteness of 70% or more before molding may be used.

[0018] In the third embodiment of the method for manufacturing a molded product, in the step of adjusting the flow rate according to the flow location in the first embodiment, a temperature difference of 5°C or more may be provided inside the mold.

[0019] In the fourth embodiment of the method for manufacturing a molded product, in the step of adjusting the flow rate to create a difference in flow rate depending on the flow location, a temperature difference of 5°C or more may be provided in the molding machine that supplies the cellulose fiber composite resin to one or more gates.

[0020] In the fifth embodiment of the method for manufacturing a molded product, in the step of adjusting the flow rate to create differences in flow depending on the flow location, the surface roughness of the mold surface may be adjusted to different surface roughnesses depending on the location.

[0021] In the sixth embodiment of the method for manufacturing a molded product, in the step of adjusting the flow rate to create a difference in flow rate depending on the flow location, a plurality of gates may be used as the gates for injecting the cellulose fiber composite resin into the mold, and the flow rate of the cellulose fiber composite resin injected at each gate may be set to a different flow rate.

[0022] In the seventh embodiment, the method for manufacturing a molded product may, in the step of adjusting the flow rate to create a difference in flow rate depending on the flow location, use multiple gates as gates for injecting the cellulose fiber composite resin into the mold, and provide a difference in the timing of the cellulose fiber composite resin injected from the multiple gates.

[0023] The method for manufacturing a molded product according to the eighth embodiment may be a sequential molding method in which, in the step of adjusting the flow rate to create a difference in flow rate according to the flow location, a difference in the timing of the cellulose fiber composite resins injected from multiple gates is provided, and the later resin is injected so as to overlap with the preceding resin.

[0024] In the manufacturing method of a molded article according to the ninth embodiment, in the step of adjusting so that there is a difference in fluidity depending on the flow location, a mold consisting of a cavity mold and a core mold for molding a product shape with a change in the flow direction, which is angled at or above 1 degree in the thickness direction with respect to the flow surface of the cellulose fiber composite resin or curved surface with a radius of R1000 mm or less, is used as the mold, and in the step of injecting the cellulose fiber composite resin, when the cellulose fiber composite resin has solidified and become a skin layer with a flow rate of 0 m / s, shear heat generation may occur at the boundary between the resin and the resin-fluid core layer, and furfural, which is a browning component, may be generated in part.

[0025] In the manufacturing method of a molded product according to the tenth embodiment, in the step of adjusting the flow rate to create a difference in flow rate depending on the flow location, a mold consisting of a cavity mold and a core mold for molding a product shape in which the thickness of the edges differs by 0.5% or more, even if it is a planar shape, is used as the mold, and in the step of injecting a cellulose fiber composite resin, when the cellulose fiber composite resin has solidified and the resin has become a skin layer with a flow rate of 0 m / s, shear heat generation may occur at the boundary between the resin and the resin-fluid core layer, and furfural, which is a browning component, may be generated in some areas.

[0026] In the eleventh embodiment, the method for manufacturing a molded article is as described above, in the first embodiment, in the step of adjusting so that there is a difference in fluidity depending on the flow location, at least one of the flow velocity, temperature, viscosity, material, and density of the cellulose fiber composite resin is different, and in the step of injecting the cellulose fiber composite resin, shear heat generation may occur, which may be accompanied by the generation of furfural, a browning component.

[0027] The method for manufacturing a molded article using a cellulose fiber composite resin according to an embodiment will be described below with reference to the attached drawings. In the drawings, substantially identical components are denoted by the same reference numerals.

[0028] (Embodiment 1) The method for manufacturing a molded article using a cellulose fiber composite resin according to Embodiment 1 of this disclosure includes the steps of: clamping a mold; injecting the cellulose fiber composite resin into a cavity in the mold from one or more gates; and, after the cellulose fiber composite resin has hardened, opening the mold and removing the molded article. In particular, the method includes the step of adjusting the cellulose fiber composite resin so that differences in fluidity occur depending on the flow location as the cellulose fiber composite resin flows through the cavity in the mold. Furthermore, in the step of injecting the cellulose fiber composite resin, the shear heat generated by the difference in fluidity as the cellulose fiber composite resin flows in the mold is accompanied by the generation of furfural, a browning component.

[0029] <Cellulose fiber composite resin> It is preferable to use a cellulose fiber composite resin in which cellulose fibers with an aspect ratio (fiber length / fiber diameter) of 5 or more are contained in a mass of 40% or more of the base resin. If the aspect ratio is less than 5, the fiber shape approaches that of powder, resulting in a low effect on improving strength, and it is also likely to cause the wood-like texture to be impaired when "fiber lifting" occurs near the surface. If the cellulose fiber content is less than 40% by mass, it is likely to result in a decrease in shear heat generation and a decrease in the amount of furfural, a browning component, making it difficult to create a significant difference in color intensity.

[0030] In this disclosure, the above-mentioned cellulose fiber composite resin is used, and molding is performed while intentionally controlling the resin temperature, mold temperature, compression heat generation, and shear heat generation so that the temperature reaches 180°C or higher, at which point the cellulose fibers begin to denature. This generates furfural, a browning component. However, it is desirable to process at 260°C or lower to prevent complete carbonization of the cellulose fibers. At that time, filling is performed from one or more gates so that a difference in flow velocity is created within the molded product. This makes it possible to achieve a wood grain finish. In particular, to produce the texture of natural wood, the mold temperature is set to a relatively low temperature (20°C to 100°C). Specifically, by setting the mold temperature to 40°C or lower, the fibers in the composite resin are prevented from sinking into the resin, and the fibers are trapped near the surface of the molded product. In this way, the natural discoloration (generation of furfural) of the natural cellulose fiber composite resin can be utilized without using colorants or other additives. Furthermore, by devising the mold structure, it is possible to obtain a molded product that exhibits wood grain (shades of color) and wood texture (fiber trapping) at the confluence points.

[0031] As the gate, a tab gate can preferably be used, which allows resin to flow into the mold from outside the product and be removed from the product after molding.

[0032] Examples of cellulose fiber composite resins that can be used in this disclosure include those obtained by pre-pulverizing bleached coniferous pulp extracted from wood to a diameter of about 100 μm and a length of about 500 μm, and then mixing the resulting powdered pulp with a base material such as polypropylene in a kneader.

[0033] When using the above raw materials, the kneader's set temperature can be, for example, 190°C. At this time, kneading can be done at a low temperature to minimize discoloration (browning) of the pulp. In addition, the shear force generated in the kneader causes defibration (unraveling of fibers and reduction of diameter), which can increase the fiber aspect ratio (fiber length / fiber diameter) in the cellulose fiber composite resin pellets after kneading compared to the powdered pulp before kneading. Pellets can be obtained by this manufacturing method, and since the cellulose fibers do not discolor due to the effects of heat, the pellets can remain white (pulp color). Cellulose fiber composite resin pellets manufactured by the above manufacturing method can be analyzed by GC / MS before injection molding, and furfural components that cause discoloration (browning) can not be detected.

[0034] <Cellulose fiber> The type of cellulose fiber is not particularly limited; any material from which cellulose fibers can be extracted, such as coniferous trees, deciduous trees, or bamboo, is acceptable. Furthermore, as mentioned above, the fibers preferably have an average aspect ratio of 5 or higher, and under this condition, the diameter can be freely selected within the range of μm to nm. To express a wide range of colors, it is preferable that the cellulose fiber is bleached and the lignin component removed, and it is preferable to use bleached pulp, which is a raw material for paper and other products.

[0035] The whiteness of pellets containing cellulose fibers may be 70% or higher as the material color before molding. Whiteness can be measured, for example, by ISO whiteness (ISO2470:JIS P 8148). Specifically, it can be expressed as the intrinsic reflectance (%) when using lighting correlated with illuminant C as the light source under indoor daylight conditions.

[0036] <Resin materials> Furthermore, the type of resin material used as the base material is not particularly limited, and any resin material can be used. However, as mentioned above, the color of the pellets after kneading changes due to the heat applied during kneading, so it is preferable to use polypropylene, polyethylene, polymethyl methacrylate, polyamide, polystyrene, etc., which can be used as the kneading machine temperature setting to 190°C or lower.

[0037] According to the manufacturing method for molded articles described herein, it is not necessary to prepare multiple types of pellets to form the desired wood texture, color variations, and wood grain. Furthermore, even when molding with an injection molding machine, it is possible to mold using a general-purpose molding machine without using special molding machines such as mixed-color molding machines or two-color molding machines. In addition, the tensile and bending properties of the molded article can be improved proportionally by increasing the amount of fibrous cellulose added.

[0038] (Example 1) Figure 1A is a schematic perspective view showing the shape of the molded product 101 according to Example 1. Figure 1B is a plan view of the molded product of Figure 1A. Figure 1C is a cross-sectional view showing the cross-sectional structure as seen in the AA direction of Figure 1A. Figure 1D is a cross-sectional view showing the cross-sectional structure of a modified example of Figure 1C. Figure 2-0A is a cross-sectional view showing the cross-sectional structure of the molten resin in the flow state in the manufacturing method of the molded product according to Example 1. Figure 2-0B is a cross-sectional view showing the cross-sectional structure of the molten resin cured after Figure 2-0A. The cross-section will be shown in detail.

[0039] Figure 1A is a schematic perspective view showing the shape of the molded product 101 according to Example 1. As shown in Figures 1B, 1C, and 1D, the composite resin to which 40% by weight of cellulose fibers are added is injected from the resin inlet, i.e., gate 102, via a runner (not shown) in the molding machine. The cylinder temperature of the molding machine is preferably in the range of 180°C to 260°C in order to melt the polypropylene base material, generate furfural, which is a browning component, and further prevent complete carbonization of the cellulose fibers. More preferably, it is in the range of 200°C to 230°C. In Example 1, molding was performed under two conditions: 200°C and 230°C. In addition, the mold temperature is preferably set in the range of 20°C to 100°C, and more preferably in the range of 40°C to 80°C.

[0040] As shown in Figure 2-0A, the composite resin injected from the gate 102 flows into the molding space 202 within the mold 201 after injection. The area where the mold 201 and the incoming molten resin come into contact is called the skin layer 203, where heat is rapidly removed by contact with the mold 201, and solidification proceeds rapidly. In contrast, the area near the center of the molten resin is called the core layer 204, where solidification proceeds more slowly than in the skin layer 203, and the resin extends and flows from the core layer 204. Finally, as shown in Figure 2-0B, the molding space 202 is filled with solidified resin. In this manufacturing process, at the boundary between the skin layer 203 and the core layer 204, the resin flow rates are different, causing shear heat generation due to shear stress. This shear heat generation generates furfural, and wood grain 205 appears inside the resin molded product after flow is complete, and the color of the composite resin becomes darker compared to other areas. Because this wood grain 205 occurs at the boundary between the skin layer 203 and the core layer 204, it is more likely to occur inside the molded product 101 rather than on its surface. Furthermore, although the wood grain 205 should ideally occur in all cross-sections of the molded product based on the aforementioned principle, the locations where it occurs at a visible level are limited. For example, near the end of the molded product, the heat of the molten resin is easily removed by the mold 201, so the skin layer 203 grows easily, and the composite resin flows while forming a visible color difference 103.

[0041] With the above configuration, the method for manufacturing molded articles according to Example 1 made it possible to mold wood-like molded articles having a natural wood texture (color variations, wood grain, and feel) equivalent to or better than that of the technology described in Patent Document 1, using only one type of composite resin containing 40% by mass of cellulose fibers.

[0042] In Example 1, a direct gate was used, but the gate shape, position, and number can be arbitrarily set within the limits of what is possible with the mold structure, and are not particularly limited.

[0043] In this disclosure, an example of a product shape prone to thermal deformation of furfural is the product end shown in Figure 1C. Specifically, it is a shape in which the angle 104 between the flow direction of the molten resin and the direction perpendicular to the plane containing the furthest product end (thickness direction) is 1 degree or more. Alternatively, as shown in the modified example in Figure 1D, it may be a shape in which the radius 107 from the reference is curved with a change in the flow direction on part or all of the curved surfaces of the surface including the gate 102, with a radius 107 from the reference of R1000 mm or less. Alternatively, even if it is a planar shape, the thickness 106 at the end may differ from the general thickness 105 by 0.5% or more.

[0044] According to the manufacturing method for molded articles described herein, it is not necessary to prepare multiple types of pellets to form the desired wood texture, color variations, and wood grain. Furthermore, even when molding with an injection molding machine, it is possible to mold using a general-purpose molding machine without using special molding machines such as mixed-color molding machines or two-color molding machines. In addition, the tensile and bending properties of the molded article can be improved proportionally by increasing the amount of fibrous cellulose added.

[0045] (Example 2) Figure 2-1A is a plan view showing the structure of the molded product 210 according to Example 2. Figure 2-1B is a schematic perspective view showing areas 211, 212, and 213 in the molded product of Figure 2-1A that contain a large amount of browning components. As shown in Figures 2-1A and 2-1B, the composite resin to which 40% by weight of cellulose fibers are added is injected in the molding machine through a runner (not shown) from the resin inlet, i.e., gates 214 and 215. The molded product 210 formed from the resin injected from these two gates 214 and 215 becomes a first region with a high proportion of browning components at the confluence 211, and a second region with less browning components and a lighter color in other parts. Similarly, the product edges 212 and 213 also become first regions with a high proportion of browning components. In other words, the furfural content differs between any first region and any second region other than the first region in the molded product.

[0046] Figures 2-1C to 2-1F are schematic perspective views showing the flow transition of molten resin in the manufacturing method of a molded product according to Example 2. As shown in Figure 2-1C, the molten resins 216 and 217 injected simultaneously from gates 214 and 215 flow into the molding space within the mold. As shown in Figures 2-1D, 2-1E, and 2-1F, these molten resins 216 and 217 spread toward the filling end, filling the molding space and forming the molded product 210.

[0047] (modified version) Figure 2-2A is a plan view of a molded product according to a modified example of Example 2, and Figure 2-2B is a schematic perspective view showing the appearance of the molded product in Figure 2-2A. As shown in Figures 2-2A and 2-2B, the two gates 221 and 222 have different widths, thicknesses, and diameters. Figures 2-2C to 2-2E are schematic perspective views showing the flow transition of the molten resin in the manufacturing method of a molded article according to a modified example of Example 2.

[0048] (1) The molten resins 223 and 224 injected from gates 221 and 222 into the molding space in the mold gradually fill the molding space (Figures 2-2C and 2-2D). (2) Ultimately, a resin molded product is formed having a first region with a high concentration of browning components due to furfural purification at the confluence 225 of the molten resins 223 and 224 and near the sides 226 and 227 of the molded product.

[0049] In Figures 2-2C to 2-2E, the shear heat generated at the confluence of the resins injected from the two gates differs compared to the case in Figure 2-1. Specifically, in Figures 2-2C to 2-2E, the fluidity of the molten resin injected from gates 221 and 222 is different. The injection speed from gate 221 is higher than that from gate 222, resulting in a difference in flow velocity and thus greater shear heat generation at the confluence interface. As a result, the color of the resin confluence 225 in Figures 2-2C to 2-2E is darker, with a higher proportion of browning components, compared to the resin confluence 211 in Figure 2-1. Furthermore, the polypropylene base material melts due to the cylinder temperature of the molding machine or the shear heat generated by the screw, producing furfural, a browning component. In addition, to prevent complete carbonization of the cellulosic fibers, the temperature is preferably in the range of 180°C to 260°C. More preferably, it is in the range of 200°C to 230°C.

[0050] (Example 3) Figure 2-3A is a plan view showing the structure of the molded product 230 according to Example 3. The molded product 230 is formed by filling molten resin through gates 231 and 232. Figure 2-3B is a schematic perspective view showing the flow transition of the molten resin in the manufacturing method of the molded product according to Example 3. (1) As shown in Figure 2-3A, gates 231 and 232 are the same size, and the timing of the inflow of molten resins 235 and 236 from both gates 231 and 232 is the same. Even in the above case, the confluence 237 of molten resins 235 and 236 may not be midway between gates 231 and 232. This situation occurs, for example, when the temperatures of the molding spaces 233 and 234 are different, resulting in different flow rates of the resins flowing through each molding space. Specifically, if the molding space consists of a molding space 233 with a higher mold temperature and a molding space 234 with a lower mold temperature, the fluidity of the molten resin will be higher in the molding space 233 than in the molding space 234. For this reason, the flow rate of molten resin 235 is faster than that of molten resin 236, and as a result, a color difference occurs in the molded product 230 at the boundary 237 between molten resin 235 and molten resin 236. Alternatively, a similar phenomenon occurs when there is a difference in the degree of polishing of the mold surfaces of molding spaces 233 and 234. Specifically, when a molding space consists of a molding space 233 with a low surface roughness and a molding space 234 with a high surface roughness, the molding space 233 has higher fluidity than the molding space 234. As a result, the molten resin 235 flows faster than the molten resin 236, and this causes a color difference at the boundary 237 between the molten resin 235 and the molten resin 236 in the molded product 230 filled with the molten resins 235 and 236. Furthermore, similar to Example 2, the first region, which contains a large amount of browning components due to the formation of furfural, is also formed near the mold wall surfaces 238 and 239.

[0051] (Example 4) Figure 2-4A is a plan view showing the structure of the molded product 241 according to Example 4. The molded product 241 is formed by filling molten resin through gates 242 and 243. Figures 2-4B to 2-4D are schematic perspective views showing the flow transition of the molten resin in the manufacturing method of the molded product according to Example 4. (1) The molded product 241 has the same size gates 242 and 243, but the height of the molded space is different. Specifically, the molded space into which molten resin flows from gate 242 is deeper than the molded space into which molten resin flows from gate 243. As a result, the flow velocity of the molten resin 244 and 245 flowing in from gates 242 and 243 along the flow direction is faster for the molten resin 245 flowing in from gate 243. Consequently, when filling the molded space, the confluence 246 of the molten resins 244 and 245 flowing in from the two gates is not located midway between gates 242 and 243, but is formed closer to the thicker section, generating furfural due to shear heating of the molten resins 244 and 245, creating a difference in color. In addition to this confluence 246, furfural is also generated near the end of the product 247 and 248 in the direction perpendicular to the plane containing the product end that is perpendicular to the flow direction and furthest away from it (thickness direction), forming a first region rich in browning components.

[0052] (Example 5) Figures 2-5A to 2-5D are schematic perspective views showing the flow transition of the molten resin in the manufacturing method of the molded product according to Example 5. (1) The gates 2511 and 2512 connected to the molding space 250 shall have the same cross-sectional shape. Molten resin flows into the molding space 250 from gates 2511 and 2512, but the timing of the inflow differs, and if the resin from gate 2511 flows first, the molten resin 251 flows in first (Figure 2-5A). (2) Subsequently, molten resin 252 flows in from gate 2512 (Figure 2-5B). (3) Molten resin 251 from gate 2511 and molten resin 252 from gate 2512 flow in in parallel (Figure 2-5C). (4) Molten resin 251 from gate 2511 and molten resin 252 from gate 2512 fill the molding space 250 (Figure 2-5D). Finally, furfural is formed at the confluence 253 of molten resin 251 and molten resin 252, and near the end of the product in a direction perpendicular to the flow direction 254 and 255, forming a first region rich in browning components. In Example 5, the flow rates of the resin entering from gates 2511 and 2512 may be the same, but if they are different, more shear heat will be generated, resulting in the production of more furfural and a greater difference in density.

[0053] (Example 6) Figures 3A to 3F are plan views showing the flow transition of the resin in the manufacturing method of the molded product according to Example 6. In Figures 3A to 3F, the molding space 301 is filled with molten resin to manufacture a molded product 306 using a mold having a gate 302 that initiates resin flow first and a gate 303 that initiates resin flow later. (1) Figure 3A shows the state in which the molten resin has not yet been injected into the molding space 301. (2) In Figure 3B, the molten resin 304 is injected from the gate 302, and the area filled with the molded product 306 made of the molten resin 304 gradually expands. (3) As the range expands, the resin flow is controlled so that after the molten resin 304 reaches the gate 303, molten resin also flows in from the gate 303, as shown in Figure 3C. This is generally called sequential molding and is a molding method used to fill the molding space 301 by resin flow from multiple gates without creating weld lines. (4) However, in the case of cellulose fiber composite resins, a skin layer is formed when the molten resin 304 reaches the gate 303, and further molten resin flows in from the gate 303, penetrating the skin layer. At this time, a large amount of shear heat is generated, producing furfural 305 (Figure 3D). (5) The molten resin spreads into the molding space 301 while furfural 305 is formed between the molten resin from gate 302 and the molten resin from gate 303 (Figure 3E). (6) Finally, the molding space 301 is filled with molten resin 304 to form a molded product 306 having a wood grain 305 made of furfural (Figure 3F). In the sequential molding of Example 6, the molding conditions that are likely to cause furfural formation as described in this disclosure are that the resin flowing in from the preceding gate is delayed by 0.1 seconds or more after reaching the gate into which the subsequent resin flows, and that the subsequent resin flows in just before the preceding resin has completely solidified. [Industrial applicability]

[0054] The molded product according to this disclosure can achieve a texture similar to real wood in a cycle equivalent to that of injection molding. Therefore, it can be applied to replace products that were previously produced using time-consuming wood carving processes, and can also be applied to the mass production of products manufactured using general-purpose injection molding machines. [Explanation of symbols]

[0055] 101 Molded products Gate 102 103 Wood grain 104 angle 105 plate thickness 106 Plate thickness change 107 Radius 201 Mold 202 Molding space 203 Skin Layer 204 core layers 205 Wood grain 210 Molded products 211 Wood grain 212 Wood grain 213 Wood grain Gate 214 Gate 215 216 Molten resin 217 Molten resin Gate 221 Gate 222 223 Molten resin 224 Molten resin 225 Wood grain 226 Wood grain 227 Wood grain 230 Molded products Gate 231 Gate 232 233 Molding space 234 Molding space 235 Molten resin 236 Molten resin 237 Wood grain 238 Wood grain 239 Wood grain 241 Molded products Gate 242 Gate 243 244 Molten resin 245 Molten resin 246 Wood grain 247 Wood grain 248 Wood grain 250 molding space Gate 2511 2512 Gate 251 Molten resin 252 Molten resin 253 Wood grain 254 Wood grain 255 Wood grain 301 Molding space Gate 302 Gate 303 304 Molten resin 305 Wood grain 306 Molded products

Claims

1. A method for manufacturing a molded article using a cellulose fiber composite resin, A step of adjusting the cellulose fiber composite resin so that differences in fluidity occur depending on the flow location when the cellulose fiber composite resin flows through the cavity in the mold, The process of clamping the mold, The process of injecting the cellulose fiber composite resin into the cavity in the mold from one or more gates, After the cellulose fiber composite resin has hardened, the mold is opened and the molded product is removed. Includes, A method for manufacturing a molded article using a cellulose fiber composite resin, wherein, in the step of injecting the cellulose fiber composite resin, when the cellulose fiber composite resin flows in the mold, shear heat is generated due to the difference in fluidity, resulting in the generation of furfural, a browning component, In the process of adjusting the flow rate to create differences in flow depending on the flow location, the mold used consists of a cavity mold and a core mold for forming a product shape with a change in flow direction, using a curved surface with a radius of 1000 mm or less and an angle of 1 degree or more in the thickness direction with respect to the flow surface of the cellulose fiber composite resin. A method for manufacturing a molded article, wherein, in the step of injecting the cellulose fiber composite resin, shear heat is generated at the boundary between the resin, which has a flow rate of 0 m / s and has solidified into a skin layer, and the resin-fluid core layer, and furfural, a browning component, is partially generated.

2. A method for manufacturing a molded article using a cellulose fiber composite resin, A step of adjusting the cellulose fiber composite resin so that differences in fluidity occur depending on the flow location when the cellulose fiber composite resin flows through the cavity in the mold, The process of clamping the mold, The process of injecting the cellulose fiber composite resin into the cavity in the mold from one or more gates, After the cellulose fiber composite resin has hardened, the mold is opened and the molded product is removed. Includes, A method for manufacturing a molded article using a cellulose fiber composite resin, wherein, in the step of injecting the cellulose fiber composite resin, when the cellulose fiber composite resin flows in the mold, shear heat is generated due to the difference in fluidity, resulting in the generation of furfural, a browning component, In the process of adjusting the flow rate to create a difference in flow depending on the flow location, the mold used consists of a cavity mold and a core mold for forming a product shape in which the plate thickness at the edges differs by 0.5% or more, even if the shape is planar. A method for manufacturing a molded article, wherein, in the step of injecting the cellulose fiber composite resin, shear heat is generated at the boundary between the resin, which has a flow rate of 0 m / s and has solidified into a skin layer, and the resin-fluid core layer, and furfural, a browning component, is partially generated.

3. The method for manufacturing a molded article according to claim 1 or 2, wherein the cellulose fiber composite resin contains cellulose fibers at a concentration of 40 wt% or more, and pellets with a material color of 70% or more whiteness before molding are used.

4. A method for manufacturing a molded article according to claim 1 or 2, wherein a temperature difference of 5°C or more is provided within the mold in a step of adjusting the flow rate to create a difference in fluidity according to the flow location.

5. A method for manufacturing a molded article according to claim 1 or 2, wherein, in the step of adjusting so that a difference in fluidity occurs according to the flow location, a temperature difference of 5°C or more is provided in the molding machine that supplies the cellulose fiber composite resin to one or more gates.

6. A method for manufacturing a molded article according to claim 1 or 2, wherein in the step of adjusting the flow rate to create differences in flow rate depending on the flow location, the surface roughness of the mold surface is adjusted to different surface roughness depending on the location.

7. A method for manufacturing a molded article according to claim 1 or 2, wherein, in the step of adjusting so that differences in fluidity occur depending on the flow location, a plurality of gates are used as the gates for injecting the cellulose fiber composite resin into the mold, and the flow rate of the cellulose fiber composite resin injected at each gate is set to a different flow rate.

8. A method for manufacturing a molded article according to claim 1 or 2, wherein, in the step of adjusting so that differences in fluidity occur according to the flow location, a plurality of gates are used as the gates for injecting the cellulose fiber composite resin into the mold, and differences are provided in the timing of the cellulose fiber composite resin injected from the plurality of gates.

9. The method for manufacturing a molded article according to claim 8, wherein in the step of adjusting so that differences in fluidity occur according to the flow location, a difference is made in the timing of the cellulose fiber composite resin injected from the plurality of gates, and the later resin is injected so as to overlap with the preceding resin in a sequential molding process.

10. In the process of adjusting the flow rate so that differences in flow occur depending on the flow location, at least one of the flow velocity, temperature, viscosity, material, and density of the cellulose fiber composite resin is made different. A method for manufacturing a molded article according to claim 1 or 2, wherein, in the step of injecting the cellulose fiber composite resin, shear heat generation occurs, resulting in the generation of furfural, which is a browning component.

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